Sadly, despite legal protections that do exist in some places to prohibit discrimination on the basis of sexual orientation, discrimination still quietly happens.
I consider myself "out". I do "come out" to people with whom I work, but I always remember that these people are first and foremost professional colleagues. Friendships may develop, but that only happens over time.
I do not make sexual orientation nor sexuality a topic of workplace conversation. These topics and aspects of the nature of people are generally not relevant to most position descriptions. There may be exceptions (i.e. A position that is specifically targeted towards "Diversity" initiatives). Generally, talk of sex and sexually oriented topics are inappropriate in most professional workplaces.
With that said, now let us consider "lunch breaks", "after work gatherings", and other situations where/when we are not in the workplace and on our "own time". From my experience, sharing aspects of one's personal life is an important part of building relationships (both personal and professional). Which aspects of personal life are shared (and when) is IMHO a personal and private decision to which every person has a right. My reality of experience with other people has indicated that it is possible to share too much information that can be detrimental to relationships and to your professional endeavors. I have experienced professional situations where after I have shared that I am gay, that I have been quietly pushed out of my job. As wrong as it was, there is little court-room admissible evidence that could support a complaint alleging discrimination based on sexual orientation.
So, I now ask myself some questions before I reveal aspects of my personal life or my opinions on controversial topics:
What do I have to potentially gain by sharing this information about me or my opinion?
What do I have to potentially lose by sharing this information about me or my opinion?
What do I know about the values, ideals, and personal opinions of the person(s) with whom I may share information about me or my opinion?
Will any or all of them be judgmental?
Could I alienate or make an enemy with any or all of these people?
In situations where/when I have been asked a question, and I would prefer not to share personal information or opinions, I respond with a degree of diplomacy and tact that befits how the question was asked. If the question was asked in passing, in private, or open to a group I may answer with a certain amount of reserve. If a question was asked in a pointed manner, or directly to me in public with others present, I may answer with a bit less reserved manner.
Here are some "stock answers" that I give in response to questions like "Are you gay?" to which I prefer not to answer. These answers are usually accompanied by direct eye contact and delivered with "command presence" and perhaps with a slight smile or look of surprise.
"I beg your pardon!?"
Depending upon how forcefully you wish to punctuate your message and terminate further discussion of this topic, you might add:
"This kind of question is inappropriate and offensive. I am going to pretend that I did not hear what was just said." Then, change the topic or politely close the conversation and leave.
If asked my opinion on a controversial topic on which I do not care to share an opinion, I might respond with:
"I have no opinion to share on this issue."
"I do not have enough information to have an informed opinion."
If I would like to know how the other person views the issue, I might then ask:
"Can you share with me your thoughts, or what you know. I'm interested in learning more."
So, there are ways that you can avoid answering the question or stating an opinion if you wish to keep your privacy. You can do so in as diplomatic and tactful a manner as you wish.
Or, you can just state your answer or make a stand with your opinion with full knowledge of the risks as another way to make a point.
In choosing to be more open or private, you may find yourself "paying a price" ether way.
Aloha and Be Well!